Multilayer optical film polarizers are known. Such polarizers comprise a plurality of distinct optical layers arranged into optical repeat units across the thickness of the film. In a simple case the optical layers, which number in the tens, hundreds, or thousands, alternate between a first and second light transmissible material in a quarter-wave stack, such that the optical repeat unit consists essentially of two optical layers of equal optical thickness. FIG. 1 shows a perspective view of one such optical repeat unit 10 in the context of a right-handed Cartesian x-y-z coordinate system, where the film extends parallel to the x-y plane, and the z-axis is perpendicular to the film, corresponding to a thickness axis. The optical repeat unit 10 includes adjacent optical layers 12, 14. The refractive indices of the individual layers 12 are denoted:n1x, n1y, n1zfor polarized light whose electric field vector oscillates along the x-, y-, and z-axes respectively. In like fashion, the refractive indices of the individual layers 14 are denoted:n2x, n2y, n2z.In most multilayer optical film polarizers, the materials and processing conditions are tailored to produce, between adjacent optical layers, a refractive index mismatch along one in-plane axis and a substantial match of refractive indices along an orthogonal in-plane axis. If we denote the magnitude of n2−n1 along a particular axis as Δn, these conditions can be expressed as:Δnx≈largeΔny≈0A film with these properties reflects normally incident light of one polarization and transmits normally incident light of an orthogonal polarization.
Jonza et al. have recently described another type of multilayer polarizing film, coined the “p-polarizer”. See e.g. U.S. Pat. No. 5,882,774 (Jonza et al.), “Optical Film”. In this construction, the in-plane indices of the two materials are equal, but the z-axis indices differ. In this case, no reflection occurs for s-polarized light at any angle, and the reflectivity for p-polarized light increases monotonically with increasing angle of incidence. This type of article has increasing reflectivity for p-polarized light as angle of incidence increases, and is transparent to s-polarized light.